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Cabinet boxes- does joinery matter? $$ ?

Posted by jaydubya (My Page) on
Sat, May 14, 11 at 22:46

For custom kitchen cabinet plywood boxes, is a screw and glue joint sufficient or strong enough, or should I pay 30% more for a CNC mortise and tenon cabinet box. Is the mortise and tenon overkill? Company A $10,700; Company B $13,900

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RE: Cabinet boxes- does joinery matter? $$ ?

It's hard to imagine a mortise and tenon joint being used to join a box at its corners. Even in fine furniture that doesn't gain strength by being screwed to the wall and to neighboring pieces of furniture, M&T is not what you'd use. So I suspect that it's a stretch to call whatever this company is doing 'mortise and tenon,' and I'm confident you don't need it.

That said, we really don't have enough information to evaluate the glue and screw joint either. We don't know the materials being used, their thicknesses, the type and size of screws, etc.

RE: Cabinet boxes- does joinery matter? $$ ?

Screw & Glue cabinets are 9 ply 3/4" birch plywood. I think he said 1/2" backs, although I would think you might want a beefier back for frameless construction. I don't know about the size and type of screw-- I'll ask about that.

I was kind of wondering about the use of the M&T term. I was thinking it would be more rabbet dado. The manufacturing process is called a nested approach and uses a CNC machine.

RE: Cabinet boxes- does joinery matter? $$ ?

Okay, rabbet/dado makes more sense. I would say that rabbets and dadoes do suggest a better cabinet than glued and screwed butt-joints. I probably would pay the difference to get the rabbeted / dadoed cabinets.

"Nested" & "CNC" are terms that you, as a consumer, have no reason to care about; they are relevant to the manufacturer and his particular business model, but they do not inherently affect the product you'll receive.

RE: Cabinet boxes- does joinery matter? $$ ?

Are you sure the first guy just uses butt joints? Not dados?

RE: Cabinet boxes- does joinery matter? $$ ?

Glued and screwed butt joints would be preferrable to stapled and not glued rabbeted joints.

That being if the glue is used in a wood product to wood product union---and not the wood edge glued to a laminated surface. This would be the case if the back piece of the cabinet were finished before installing in a rabbet. The glue would do little good since it will not bond with the surface of the finish on the back piece.

My point is there are lots of words used to seem hi tech----when low tech is often MUCH better. Low tech would be to build the cabinet and then finish---but that method is pretty much out of practice for most stock cabinet making, since it makes the finishing much more difficult and expensive.

Having said all that, the properly rabbeted back variety would also be my choice of the two, since the rabbet does provide more structural stability if done with finished materials.

Now you are probably more confused.

RE: Cabinet boxes- does joinery matter? $$ ?

"'s hard to imagine a mortise and tenon joint being used to join a box at its corners."

M&T are not used to joint the edge of panels like plywood.

A rabbet (groove with one side open) or a housed dado (both sides of groove closed) are used.

The screws are more of a manufacturing convenience than a real strength increase.
Modern glues are already stronger than the wood, and the screws serve mostly to clamp the joint during setting of the glue.

RE: Cabinet boxes- does joinery matter? $$ ?

I too like the idea of the rabbeted joint, certainly more glue surface area. CNC could create very precise joint. But paying over $3,000 ($10,700 v. $13,900)????

Our current cabinets are just naile and glued plywood -- they are over 50 years old and they are still fine

I think my question should be: Will the srew and glue boxes last another 50 years (I'll be 100)??

I guess it depends on the screw, but in my experience I have found that screws give substantial holding power and sheer strength, especially into a 9 ply plywood. I know glues are improved, but I also fid it hard to imgine that a 90 degree glued butt joint would fail anywhere but the joint

RE: Cabinet boxes- does joinery matter? $$ ?

It's entirely possible to make a glued and screwed joint that will last just fine in a kitchen cabinet. It's also possible to do it wrong, by using the wrong sort of screws, drilling the wrong size pilot holes, or not using enough screws. So we can't definitively say whether the particular results you'd get from the guy you're talking to will be good or bad. I think we can say that it takes surprisingly little to hold a kitchen cabinet together once it's installed. They are not subjected to the stresses that freestanding furniture suffers whenever someone decides to rearrange a room, and they gain considerable strength from the walls, floor, countertop and neighboring cabinets to which they are attached.

I also fid it hard to imgine that a 90 degree glued butt joint would fail anywhere but the joint

You're right about this. In my opinion, the idea that 'modern glues are stronger than the wood' is frequently applied in contexts where it doesn't make any sense.

RE: Cabinet boxes- does joinery matter? $$ ?

"hard to imgine that a 90 degree glued butt joint would fail anywhere but the joint"

It will break near the joint, but the glue line should hold.

The broken surface will normally remove some of the ply from the perpendicular surface since the glue is stronger than the wood.

Depending on the direction of the forces, the screws may simply burst through the surface or the small section of wood from the side of the screw to the edge of the plywood will simply break out under the point loading of the screw shaft.

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